title: Efficiency of light-driven metabolite transport in the photosynthetic bacterium Rhodospirillum rubrum.
abstract: An evaluation of the efficiency of the L-alanine and L-malate transport systems was undertaken with the photosynthetic bacterium Rhodospirillum rubrum grown on the amino acid whose uptake was measured. An all-glass apparatus was constructed for measuring transport activity under anaerobic conditions. L-Alanine transport activity decreased under conditions of Mg2+ depletion. When cells were allowed to become inactive by suspending them in the dark in Mg2+-free buffer, full activity could be restored with a few minutes by adding 20 mM Mg2+ and illuminating the cells. The transport activity was completely inhibited by carbonyl cyanide m-trifluoromethoxyphenylhydrazone and by ammonia. The quantum yield for the uptake of either L-alanine or L-malate was 0.015 molecules per photon. The results are discussed in relation to the expected efficiencies for metabolite transport and regulation by Mg2+.
mesh_terms: D000409:Alanine / Q000378:metabolism*; D000968:Antimycin A / Q000494:pharmacology; D001693:Biological Transport, Active / Q000187:drug effects / Q000528:radiation effects; D004024:Dicyclohexylcarbodiimide / Q000494:pharmacology; D004579:Electron Transport; D007700:Kinetics; D008027:Light; D008274:Magnesium / Q000494:pharmacology; D008293:Malates / Q000378:metabolism*; D009840:Oligomycins / Q000494:pharmacology; D010100:Oxygen / Q000494:pharmacology; D012247:Rhodospirillum rubrum / Q000378:metabolism*
chemical_list: D008293:Malates; D009840:Oligomycins; D004024:Dicyclohexylcarbodiimide; D000968:Antimycin A; C030298:malic acid; D008274:Magnesium; D000409:Alanine; D010100:Oxygen